| 摘要 |
PURPOSE:To eliminate a DC offset in excellent way with simple constitution by using a different value of differential currents for a differential buffer circuit of a delay circuit used for a ghost eliminating device so as to suppress a DC level fluctuation. CONSTITUTION:Transistors (TR) 114a, 114b of a buffer circuit at input side are connected to an input terminal 113 of a delay circuit and a phase shift circuit comprising a TR104, a resistor R4 and a capacitor C is connected to the buffer circuit. Further, buffer circuits each having a phase shift circuit comprising TRs 118a, 118b, a resistor and a capacitor are connected in cascade to the phase shift circuit so as to form the 1st stage. The buffer circuits of the constitution above are connected by plural number of stages in cascade. Each buffer circuit is provided with TRs 122, 123a and 123b or the like constituting a current source, and the ratio of r' to r'' of the current source is unbalanced to another so as to unbalance currents I1, I2 flowing to the TRs 123a, 123b thereby suppressing the fluctuation in the DC level. Then, the DC offset is eliminated with simple constitution.
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